Short hard math riddles

99 / .99 or 99 + 9/9

Just once, because after you subtract anything from it, it's not 25 anymore.

Two. The inside and the outside.

688. Add the two previous numbers and multiply by 2.

Yes. 10 o'clock + 4 hours = 2 o'clock.

F I V E. Remove the 2 letters F and E from five and you have IV.

111111111 Explanation: It's a maths magical square root series as : Square root of number 121 is 11 Square root of number 12321 is 111 Square root of number 1234321 is 1111 Square root of number 123454321 is 11111 Square root of number 12345654321 is 111111 Square root of number 1234567654321 is 1111111 Square root of number 123456787654321 is 11111111 Square root of number 12345678987654321 is 111111111 (answer)

SIX - 9 (IX) = S 9 (IX) - 10 (X) = I 40 (XL) - 50 (L) = X

Cut 1: Cut the pizza straight down the middle into two halves. Cut 2: Keeping the two halves in the place, cut the pizza straight down the middle at right angles to the first cut (you will be left with 4 equal quarters) Cut 3: Pile the 4 quarters on top of each other and cut through the middle of the pile. You will be left with 8 equal slices.

Each number in the sequence is a representation of the number 32 in different bases, starting with base 10.